Performing high-resolution ultrasonic thickness mapping of complex shapes with changing geometries, such as elbows, bends, nozzles, or any part with variable geometry is very challenging. To map the thickness of such components, conventional ultrasonic probes must be held perpendicular to the surface at every point of data acquisition. This process is slow and corrosion pits can be missed between acquisition points. Using ultrasonic phased array probes allows large areas to be rapidly scanned at high-resolution, but standard linear phased array probes are rigid and cannot conform to changes in component geometry.
When performing NDT/NDI with a phased array probe, the ultrasonic focal laws must be arranged so the propagation direction of the beam is perpendicular to the test object surface. Such inspection is usually done using local immersion by means of a water wedge, in which water is used as the coupling medium between the probe and the test object. However, any other suitable coupling medium may also be used. To ensure that the propagation direction of the beam is perpendicular to the test object surface, the probe curvature must substantially match the part curvature. In existing practice a flat probe array may be used for a flat surface, whereas for a pipe a custom probe must be made for each pipe diameter, and complex custom probes must be manufactured for complex part surfaces.
Manufacture of custom wedge designs is possible at reasonable cost using standard machining or 3D printing techniques. However, design and manufacture of custom probe array geometries is only possible with long manufacturing lead times and at great expense.
US patent application 2015/0219602 discloses a wedge for a flexible ultrasonic array, in which inspection of a curved surface is done by inserting the flexible array between two detachable parts of the wedge. However the wedge, having two parts, is complex to manufacture, requires tools to disassemble and assemble, and is inconvenient and time consuming to use.